Electrostatic recorder with electrodes arranged inside of a hollow type roll

ABSTRACT

A HIGH SPEED ELECTROSTATIC PRINTING MECHANISM INCLUDING A HOLLOW TYPE ROLL PRESENTING A CONCAVE MATRIX OF RAISEDFONT ELECTRODES CONFIGURED A DIFFERENT ALPHA-NEMERIC PRINTCHARACHERS. IN ONE EMBODIMENT ROWS OF CHARACTER-FONT ARE PRESENTED, EACH ALONG A RESPECTIVE CONDUCTIVE STRIP, THESE STRIPS BEING ELECTRICALLY-INDEPENDENT AND SURROUNDING AN INNER ROTATING DRIVE ROLL PROVIDED TO ADVANCE DIELECTRIC RECORDING MEDIA PAST THE STRIP MATRIX TO BE SELECTIVELY CHARGE-IMAGED. THE ELECTROSTATIC TRANSFER-POTENTIAL APPLIED ACROSS SELECTED &#34;PRINT-AREAS&#34; OF THE DIELECTRIC CAN BE ARRANGED TO (ELECTROSTATICALLY) IMAGE, EITHER &#34;LINE-BY-LINE&#34; (DRIVING A RECORD REPEATEDLY PAST THE MATRIX, ONE PASS FOR EACH LINE), OR &#34;BY-THE-PAGE&#34; (PROVIDED SUFFICIENT MEMORY STORAGE AND FAST-SWITCHING MEANS ARE AVAILABLE). THE DIELECTRIC IS THEREAFTER DEVELOPED AND COPIED AT A TONER/ TRANSFER STATION.

Feb. 16, 1971 E. MASTERSQN ETAL 3,564,559

ELECTROSTATIC RECORDER WITH ELECTRODES ARRANGED INSIDE OF A HOLLOW TYPE ROLL Filed Nov. 1. 1967 4 Sheets-Sheet 1 T v L m a l m. L

f INVENTORS, EARL E. MASTERSON :1: DAVID w. BERNARD MICHAEL S. SHEBANOW I BY K L '7 ATTORNEY Feb. 16, MASTERSQN ETAL 3,564,559

ELECTROSTATIC RECORDER WITH ELECTRODES ARRANGED INSIDE OF A HOLLOW TYPE ROLL Filed Nov. 1, 1963" 4 SheetsSheet s 7 /SA /CS 86-! H /SG-2 ABCDEFG L YQfiCD (5/85 H A500 ab LB-2 I I 1 I I I L U j 1 H .h PM A/ PR FIG. 4

CR DM L-l FIRSTL/NE FIRST L/A/E Second L/NE Second L/A/E 7/3/90 L/A/E 72/20 L/Mf FIG. 5

INVENTORS. EARL E. MASTERSON DAVID W. BERNA D ATTORNFY Feb. 16, 1971 E MASTERSON ETAL I 3,564,559

ELECTROSTATIC" RECORDER WITH ELECTRODES.ARRANGED INSI DE OF A HOLLOW TYPE ROLL Filed'Nov. 1, 1967' 4 Sheets-Sheet 4 INVENTOR. EARL E. MASTERSON DAVID w. BERNARD F I G 7 Y MICHAEL s. SHEBANOW ATTORNEY United States Patent US. Cl. 34674 21 Claims ABSTRACT OF THE DISCLOSURE A high speed electrostatic printing mechanism including a hollow type roll presenting a concave matrix of raisedfont electrodes configured as different alpha-numeric printcharacters. In one embodiment rows of character-font are presented, each along a respective conductive strip, these strips being electrically-independent and surrounding an inner rotating drive roll provided to advance dielectric recording media past the strip matrix to be selectively charge-imaged. The electrostatic transfer-potential applied across selected print-areas of the dielectric can be arranged to (electrostatically) image, either line-by-line (driving a record repeatedly past the matrix, one pass for each line), or by-the-page (provided sufficient memory storage and fast-switching means are available). The dielectric is thereafter developed and copied at a toner/ transfer station.

INVENTION FEATURES In the high speed printer art, as adapted for computer print-out or the like, Workers have long tried to eliminate the impacting mechanisms of conventional printers for several important reasons, such as for noise reduction, increasing print speed, eliminating manufacturing and maintenance problems associated with moving mechanical elements (striking elements, linkages, etc.) and so on. As a result, some Workers have turned to electrostaticimaging as a solution; representative efforts being disclosed, for instance, in US. Patents 2,919,967 and 3,045,- 5 87, both to Schwertz, and US. 3,182,333 to Amada et al. Some prior art efforts have involved impressing an electrostatic image on a photo-conductive medium; where, for faster imaging, others have turned to electro-printing (sometimes called Tesi-printing) whereby a latent electrostatic charge pattern is deposited on an insulating recording medium by virtue of an ionizing field discharge between two electrodes, one electrode being shaped as a prescribed (one of a set of) character. Of course, the imaging medium must be a sufliciently good dielectric not to break down upon application of the image-charge until the image transfer is effected, this being done, typically, by application of a relatively low voltage triggering pulse to one or both electrodes surrounding the dielectric. Electronic switching circuits and memory elements are typically contemplated for selectively printing in accordance with information received; for instance, from a digital computer (printer control) source. Typically, these images are developed with toner and thereafter transferred (electrostatically, preferably; or by contact) to copy paper. Some less desirable systems apply a corona charge to the transfer sheet, though this can degenerate the electrostatic image due to the breakdown of the air layer between the sheet and the dielectric. A cautionary observation is that when the dielectric and transfer sheet are in virtual contact, the air film separation between them is so small (from a few microns to a few mils) that an extremely high potential is required to trigger air-breakdown; but as this spacing increases, much smaller fields can initiate break- 3,564,559 Patented Feb. 16, 1971 ice down (ion avalanching) and badly distort the latent electrostatic image, making it unacceptable for re-use.

Prior art forms of electroprinting, such as those aforementioned, have typically involved the use of raised font character-electrodes in the form of a cylindrical type wheel or drum, the font being distributed circumferentially thereabout in the manner of conventional high speed (impact) printers. According to the present invention, however, such a character-electrode array is presented in a hollow type roll configuration, being distributed uniformly about a regular concave font-(imaging) plane, along which dielectric recording media can be swept for imaging thereon. Thus, the font-array is stationary and need not be rotated or commutated, etc.; and as a consequence, is also operable with a smaller, more compact transport (imaging) drum (or the like) within this plane. Those skilled in the art will recognize several important advantages accruing to such a hollow type roll feature, such as improved access to the character-electrodes, since they may be presented directly to external connections, whereas with prior art configurations, they would be necessarily accessed through a continually rotating drum, this involving some rather nasty complications, such as how to arrange intra-roll conductors, how to insulate them and lead them out through a rotating hub, plus commutation problems associated with applying power along multiple parallel lines through a revolving hub, etc. Another advantage recognized will be that a more convenient, compact font array is presented for page-imaging; this generally being impractical with a conventional type roll. An associated advantage is that this arrangement provides a very convenient means for line-at-a-time imaging, such as on unit record dielectric media, imaging one line with each rotational pass about a transport drum. Yet another important advantage is that a dielectric coated drum may be used as the recording medium for the hollow type roll array whereas this is impractical with conventional type rolls.

According to another feature of the invention, the aforementioned raised-font characters are provided on a set of electrically separate conductor strips, arranged in parallel along the concave font-plane to define the imaging zone. Dielectric record media are swept past successive character strips in electrostatic imaging relation therewith. In this fashion, image-media are made to scan the character font, rather than vice versa, as is conventional (for instance, with prior art type rolls). The embodiment of FIGS. 1 and 2 is an example of this and workers in the art will appreciate its advantages, such as in reducing switching problems, all characters along a given strip being energized together, at a given time. This arrangement will also better maintain vertical (print image) alignment (e.g. in the manner of a chain printer), vertical misalignments being more noticeable and offensive to printing connoisseurs than horizontal, of course.

According to another feature of the invention, unit record dielectric media may be provided as opposed to the conventional continuous media (such as an endless web, coated-drum, etc.) for apt use with such a hollow type roll. As described below, particularly in connection with the embodiment of FIG. 1, such a unit record dielectric allows the convenience of selecting multiple (rotational) transfers past the imaging station (e.g. on a drum for imaging successive lines with each pass) as well as for individual handling of the image medium after imaging, such as for asynchronously developing and copy-transferring the image, for multiple copy-transfer passes asynchronous of imaging operations, and for storage of this medium as a master (developed or not) for further use (e.g. later use as an inking master, later modification (updating) of the image, or the like).

Workers in the art will also recognize that the capability for such a multi-pass imaging mode requires only a serial, character-by-character logical control for printing a line at a time (one for each pass), thus making serial-toparallel electroprinting (serial memory inputparallel copy-out) practical and attractive, as well as eliminating the usual complex serial/parallel conversion means and requiring no form-advance time (since there is no need to incrementally step the (paper sheet) medium).

. Therefore, it is an important object of the present invention to provide a non-impact, electrostatic high speed printing mechanism for computer printout and the like. It is a related object to provide such a mechanism with the aforementioned features and advantages and solving the aforementioned problems. Another object is to provide such a printing mechanism for Tesi-printing, presenting raised-font character electrodes as a stationary array along a concave plane for imaging upon passing record dielectric media. A related object is to arrange such an array to comprise a parallel array of commoncharacter electrode-strips and to arrange for the transport of the dielectric past each strip successively for a successive scanning of charatcer-rows by the medium. A related object is to provide such an array of character electrodes in a manner apt for line-by-line imaging or page-imaging of a dielectric and allowing multiple transfer passes of the dielectric where desired.

Another object is to provide a hollow type roll imaging array in conjunction with a rotating dielectric-coated drum adapted to record and transport electrostatic images for print-out. Yet a further object is to provide such an array of character font whereby a complete set (or a plurality of dilferent sets) of characters is presented along a single common electrode, one such electrode being provided for each print line in a prescribed page-format so that print lines may be imaged serially and thereafter copy-transferred (e.g. as a page) in parallel. A related object is to provide such strips so as to be adjustably spaced for convenient control over variable spacing between print lines.

Other'objects and advantages will appear as the description proceeds. In accordance with one embodiment of the invention described in detail below, a stationary matrix of font-electrodes is arrayed along a prescribed concave imaging plane for Tesi-printing of a page of print upon a prescribed dielectric, continuously advanced repeatedly therepast, one line with each pass.

For a better understanding of the invention as well as other objects and further features thereof, reference should be had below to the following detailed description of preferred embodiments thereof, together with the accompanying drawings, wherein like reference symbols denote like parts and wherein:

FIG. 1 is a very schematic perspective of an electroprinting embodiment comprising a hollow type roll imaging station and a developing copy-station together with schematically-indicated dielectric imaging media and associated transport means for advancing the media through the stations;

FIG. 2 is a plan schematic view of an imaging array like that in FIG. 1 and illustrating a set of like character-electrodes and an orthogonal set of columnselecting electrodes, these sets being spaced to imagingly suround an intermediate representative dielectric medium; FIG. 3 is a very schematic showing of an alternate electro-printing arrangement;

FIG. 4 is a schematic fragmentary plan view of (a representative portion of) a set of character-electrodes alternative to that in FIG. 2;

FIG. 5 is a representative illustration of typical imagingtransfer operation of an electrode array like that in FIG. 4, indicating a serial-imaging of a dielectric together with a parallel print-out therefrom;

FIG. 6 is an upper isometric, schematic showing of an electro-printing embodiment alternative to that in FIGS. 1 and 3;

FIG. 7 is a side-sectional schematic showing of representative portions of the arrangement in FIG. 6 rotated from the position shown in that figure; and

FIG. 8 is a fragmentary sectional view of a typical dielectric medium surrounded by a representative-raisedfont electrode and, orthogonal thereto, a plurality of column-select electrodes.

Referring now to the electro-printing embodiment of 'FIG. 1, it will be understood by those skilled in the art that this l system generally comprises an electrostatic imaging station 1 through which prescribed dielectric media MS (shown here as a unit record for which this embodiment is quite apt; however, endless web or other forms may also be used, as seen below) will be understood as transported to be swept past a number of stationary, raised-font character-imaging rows to generate one or several lines of selectable electrostatic print images thereon. Image media MS are understood as thereafter transported (by means not shown, but well-known in the art) along transport path P to an output station OS whereat to be suitably developed, toned and brought into copy-transfer relation with copy media CR.

More particularly, and according to one feature of the invention, imaging station 1 will be seen as comprising a hollow type roll aray 1-S of raised-font (charactershaped) electrodes disposed in a set of parallel, regularlyspaced, electrode strips 1SA, l-S-B etc. through L-S-N (latter being for terminal symbol), being parallelarrayed along a prescribed concave (cylindrical) electrode plane. As seen better in FIG. 2, each strip is electrically insulated, having a prescribed electrode terminal 2, and presents a respective raised-font electrode surface, disposed along the electrode-plane in (printing) column-registry, as understood in the art, with like-character font aligned along each strip to define a character-row,

orthogonal to print-columns. Within this electrode plane, and concentric therewith, is a cooperating rotatable transport drum l-S having its periphery spaced along a prescribed ground-plane coplanar with this electrode-plane and spaced a prescribed (ionizing) gap distance from the raised surface portions of character electrode array l-S suflicient that the interposition of medium MS (of prescribed materials, dimensions etc.) will establish a prescribed dielectric/electrode imaging gap (between the dielectric surface of the medium MS and the raised-font portions as well understood in the art and further described below 'with reference to FIG. 8). Drum l-S is kept continually rotating (by conventional means, not shown) so as to sweep each dielectric sheet MS one or several times (selectively) past electrode array 1S at a prescribed, constant speed and continuously. Although other means known in the art may also be used, drum 1S' is preferably adapted to engage records MS vacuumatically by provision of vacuum ports along the periphery thereof (not shown, but well-known in the art), the vacuum thereto being supplied (by a conduit through hub 1-S'-H) from a conventional vacuum system, schematically indicated as VAC. The details of this and other analogous engagement means are well known in the art and need not be further dwelt upon.

Electrostatic imaging sheets MS are shown in unit record form but may be otherwise comprised (e.g. a Mylar web) of any suitable dielectric medium capable of retaining an electrostatic image long enough for subsequent utilization (e.g. transfer to another surface, development, copy-transfer, etc.). Typically, such a medium MS comprises a multi layer composite, as shown sectionally and fragmentarily, in FIG. 8, having a dielectric layer md mounted (for physical support, manufacturing convenience, etc.) upon a relatively low-resistance backing mb such as a layer of paper-fabric or the like. An exemplary raised-font character electrode 1SA (for the character A, see FIG. 2 also) is shown as presenting a few raised electrode surfaces spaced a prescribed dielectric-gap d-g from the confronting surface of dielectric layer md (image-plane) so that upon application of a prescribed select (imaging) potential V therebetween (e.g. to strip 1SA) an ionizing discharge will take place across the air-gap d-g therebetween to electrostatically image certain raised portions of 1SA (lying opposite a charged ground-strip 1S) on the confronting portion of dielectric md as known in the art. A number of representative ground-electrode strips (or row-electrodes) 1S'1, 1S2, 1S'3 are also shown, each being disposed opposite a respective raised-font character, each being about a character-wide and parallel, being spaced a prescribed electrode-gap distance e-g therefrom. Thus, with a prescribed inter-electrode potential (V (e.g. character pulses) across selected strip-pairs (such as 1SA and 1-S'-3 for imaging an A character image on that portion of layer md therebetween at a particular time) the desired electrostatic imaging may take place as known in the art.

In this connection, however, it is preferred that the media MS dispense with substantially all such low-resistance backing mb thereon and that the contact-surfaces of ground-strips 1S be brought practically tangent to dielectric layer md (as indicated by the dotted lines in FIG. 8), or that means be otherwise provided so that if potential V is applied to one or more of electrodes 1S'/1S the field from 1S will not be so conducted through any intermediate low-resistance layer like mb as to distort or degrade the resulting electrostatic image on the intervening dielectric layer md, not be diffused, or laterally-spaced, orthogonal to gap e-g. An alternative, less practical, expedient is to provide high-dielectric stripes between inter-electrode portions of a backing like mb, registering this so that the problematical lowresistance portions occur only in registry with electrodes 1S.

It will be apparent from the foregoing, and especially from a consideration of FIG. 2, that imaging station 1 is intended to be capable of imaging a prescribed array of alpha-numeric symbols as well as special symbols, decimal digits, mathematical characters, and the like, comprising a set of like-character electrode strips ISA through 1SN (e.g. 1S-2 in FIG. 2), one strip for each symbol. Although it may be otherwise implemented, according to a feature of this embodiment, the imaging station 1 arranges this array of character-strips (-electrodes) 1S so that each corresponds to a particular character (on MS, along column direction C-C, in parallel) and arranges orthogonal ground-strips 1S so that each corresponds to a particular print-line (or row on MS, aligned in parallel along C0-C0). This transport-imaging arrangement effectively provides a character-array which is scanned, column-by-column, by advancing medium MS (indicated by arrow; for example for imaging successive print-lines with each pass around drum 1S; or, alternately, imaging all lines in parallel if the memory, switching etc. is available). The imaging-potential V is preferably applied at a particular column position of MS (impressed thereacross) at the instant that position is confronted by the appropriate character-electrode 1S corresponding to the character to be printed there. (The selection logic switching and signal supplying means, in general, are well understood in the art and assumed to be conventionally supplied here. Thus, they are not illustrated in detail.)

Imaging potential V will be understood as that gappotential (in effect, between the electrode-plane (fontplane) and the confronting dielectric surface (or imageplane; see gap d-g, FIG. 8; typically about 12 mils or less) which is sufficient to effect the "imaging? aforementioned. Preferably, however, a prescribed opposite potential will first have been applied along the respective ground strip (row electrode) 1S corresponding to the 6 subject print-line (on MS) so that each selected character strip 1S (corresponding to registration thereof with the column for its characterat registration-time) may be pulsed to raise the gap-potential to V at that time only. With a respective row electrode at ground, a pulse of about -l000 volts for about 50 ,usec. on a selected character-strip has been used effectively (producing a negative electrostatic image, of course, which must be developed With a positive toner as known in the art). The potential necessary for imaging will depend, of course, upon the characteristics of the medium MS (should be as thin as possible, e.g. one-half mil or less; with high dielectric const.) its speed, etc. as known in the art and may be developed in a number of other ways. For instance, part of V may be developed on the row-electrode 1S (e.g. +500 volts, AC being used if a half-cycle is within transfer time; may provide help in synchronizing also) and part on the selected character strip (e.g. 500 volts); or this strip part-potential (e.g. 500 volts) be applied prior to registration-time whereat another additive voltage (step) may be synchronously applied (e.g. 500 v. step. Also, the image-polarity may be reversed (e.g. +1000 v. on character strip for positive image on MS, requiring negative toner). Further, it may be advantageous to charge the dielectric, itself, in certain cases, such as by corona charging (e.g. to about +300 v., with the character strip at 800 to l000 v.) this theoretically providing superior toning (good background, opposite charge to image), while, however, introducing the problem of satisfactorily erasing the image and recharging. A further advantage to such medium-charging is that Where only the print-line (row) area of the dielectric is charged, it can help to assure registration of the image therealong.

Thus, in FIG. 2 an array of parallel common-character strips, 1SA through 1S-2, are shown in a representative plan view and schematically, each strip being coupled to an associated energizing conductor-terminal t. Strips 1S are arranged in parallel to define the prescribed fontplane (concave as indicated in FIG. 1), although it will be understood that this arrangement is merely illustrative of the invention and that a greater or lesser number of character-strips (and row-strips) may be used depending upon the associated number of symbols (and print-rows) employed. Interposed between these strips arrays is (schematically shown) a passing dielectric medium MS, being understood as in-transport (in the direction of the arrow) to sweep past successive column-electrodes 1S continuously. (The plan view is from the character electrode side or from within drum 1S; the array having been shown in rectilinear rather than curved form for simplicity and clarity.)

Superposed in crosswise-matrix-(index point)-forming fashion, and on the opposite side of the path for media MS, is the aforementioned coplanar array of parallel ground-strips 1-S-1 through 1S'-N, one being provided for each (maximum) line to be printed on media MS. Each such ground-strip is provided with an energizing terminal t for application of a prescribed imaging potential, such as applied to be simultaneous with imaging a prescribed line (and with a potential to a selected one of character-electrodes 1S, associated with the image for that line, or intervening passing portion, of media MS). Groundstrips 1S are spaced a prescribed interline distance (controllably variable in embodiment of FIG. 4 etc.) while the spacing of character-strips 1S will be determined simply by the desired imaging speed (relative medium-transport speed). Of course, where the above arrangement is not preferred, the imaging may take place row-by-row rather than column-by-column, so that the column-axis CC on MS and the row-axis C0-C0 become, instead, a row-axis and a column-axis, respectively.

Thus, in operation, when a medium MS is first injected in prescribed alignment (by means not shown) into imaging station 1, it is vacuum-engaged against the continuuosly rotating transport roll comprising row-strips 1-S' and begins to sweep (sidewise in this embodimentcf. FIG. 2) column-by-column past the imaging electrodes (character-strips 1S). For simplicity of operation (minimum memory size and switching simplicity) and for relatively moderate imaging-speeds, a half-select" potential V may be applied now to the ground-strip corresponding to the first print-row (i.e. potential V on 1-S-1 is part of the necessary imaging potential V and as the columns (print-positions) of that print-line (on MS) are swept past character-strips 1-S-A through 1-S-2, each of the latter will be energized (with a complementary half-select potential V suflicient to effect imaging with complementary potential V in synchronism with registration of their column with the subject print-line. Then, medium MS may be recirculated about drum 1-S to sweep a second time past the electrode array, for imaging the second-print-line during this pass, only row-strip 1S2 being energized this time (synchronous with medium transportconventional commutation being provided for this at hub 1-S'H as known in the art) and the character-strips be. synchronously energized for respective imaging along this line, as with the first line. Conventional record-advance detecting means may provide synchronism (strobing) and control successive passes. In this manner, successive recirculations of medium MS can effect imaging of successive print-lines. Workers in the art will recognize that such a selective application of ground potential and such a repeated sweeping of a dielectric past an imaging matrix is new.

Of course, the medium MS may instead be advanced lengthwise (in direction CC, orthogonal to that shown, i.e. to arrow) and similarly imaged (one line with each pass) if the orientation of the electrode sets is rotated 90. Likewise, the array in FIGS. 1 and 2 may image in column-by-column fashion (instead of line-by-line) with obvious adjustments in Memory and Control arrangements. An array somewhat like this, but modified along'the lines of the embodiment in FIGS. 6 and 7 may image an entire page, etc. by electrically isolating each character-electrode font and adjusting Memory, controls and connections accordingly. Workers in the art may, in certain instances, dispense with individual electrodes on the transport drum (e.g. making its entire surface a continuous electrode); however, this will forfeit the recognized advantages of controlling line-by-line imaging in successive medium-passes with simple synchronized commutation means and thereby eliminating complications such as coincident energization of a second imaging electrode and the like. Further, it will be recognized that the recirculation (multiple medium-passes) this involves would not be feasible without the hollow type roll (or cylindrical font-plane) configuration; the latter also making especially advantageous use of unit record media.

Another feature of this arrangement is that, subsequent to the (alpha-numeric) variable print-imaging at station 1, unit record media MS may thereafter be fixedform-image'd electrostatically, as an option, such as by arresting them over a prescribed form-plate 2 disposed along path P, between imaging station 1 and developing station OS. Plate 2 is very schematically shown but will be understood to include a raised font (raised metal pattern) 2-F, exemplarily shown defining the image Honeywell, though it will be understood that any fixedform raised pattern may be used (or a set of them) defining any image pattern (or set). It will be understood by those skilled in the art that, with medium MS positioned-(effectively, kept stationary) in registration over plate 2, the font may be energized so that an ionizationproducing discharge may be produced to image the raised metal pattern on MS in the manner of station 1. This image may be registered with the variable information printed at.station 1 and comprise such fixed-patterns as ruled lines, captions, letterheads, etc. It will be understood as generated by applyin an appropriate potential to plate 2 (by means not shown) as understood in the art. The art will appreciate that imaging such fixed-form informa-. tion allows dispensing with the need for the usual preprinted forms in high speed print-out, the latter being quite expensive and restricting the flexibility and speed of the printer, plus wasting machine time during short runs by requiring stationary-changes, etc. Of course, using the printer to print such fixed-format information is also less feasible since it unnecessarily slows the variable printing (imaging) speed. Such fixed-form information may be made selectable, as may be contemplated, such as by providing a manually (or automatically) selectable library of fixed form layouts to be substituted for the illustrated imaging plate 2.

After imaging fixed and variable, the imaged medium MS will be transported (by any conventional meansnot shown) to output station OS whereat a prescribed transport drum D-1 is arranged to engage it and sweep it through a toning station 3 for development of the electrostatic images, then into transfer-relation with a prescribed copy sheet CR, the latter being presented, synchronously and at relatively the same speed, by an associated, drive roll D-2. Subsequent to an initial toner-transfer in this manner, the toned medium MS may optionally be immediately erased (cleaned of toner and discharged or neutralized) at cleaning station 3'. Alternatively (e.g.

for multiple copy-transfers) MS may first be recirculated by drum D-1 past toning station 3 and succeeding copy sheets CR, after which it may then be erased. Of course, a further option is to avoid cleaning the toned sheet MS entirely and, instead, store the toned pattern for future use (by means not shown). Toning station 3 may be of any suitable form known in the art; for instance, such as described in the aforementioned patent to Amada et al.; it may use a brush developer (e.g. liquid type or magnetic brush),,a spray, cascade developing etc. Although not shown, it will be understood that a conventional fixing station may be located downstream of this transferral (to sheets CR) for fixing the transferred toner image on CR, e.g. by heat fusion (such as with an IR lamp, hot gas, electric heater etc.), or using a cold-resinfix etc. Similarly, erasing station 3' will comprise any suitable cleaning-discharge arrangement known in the art.

ALTER-NATIVE STRIP-ELECTRODE ARRANGEMENT FIG. 4 shows an alternative embodiment for the character-strip array v1-S in FIGS. 1 and 2, comprising an array PR of parallel character-strips LB which will be understood as similar in construction and operation to strips 1-S aforedescribed, except as below described. Each strip LB presents one or more successive sets (styles) of raised-font character patterns for electrostatic imaging upon an associated dielectric medium, indicated schematically as DM (FIG. 5) or DM (FIG. 3both analogous to medium MS above), as the latter is advanced across array PR (arrow PM) in electrostatic imaging relation therewith. Electrode array PR may be understood as, in general, defining a font-plane as with array 1-S described above, and as operated similarly except as follows. The (one or several) sets of individually styled characters (e.g. sets SG-l, SG-Z etc. on strip LB-l) provided along the length of each character strip LB will be understood as being identical and registered, character-for-character,

on each strip. The strips LB-l, LB-Z etc. in array PR (one for each line of print) are disposed and held adjustably within a 'fixed frame CS such as to space them a regular, selectably-variable (line-) distance apart and in parallel. Thus, strips LB are preferably mounted in registry on one or more brackets A from casing CS and a resilient alignment spring SA is provided on one side (or both sides) of striparray PR to allow for spacing-adjustments between the array, as seen below.

Preferably, and according to another feature of the invention, electrodes LB are mounted and controlled to be space-adjusted, in common, for variable inter-electrode spacing. One preferred means for effecting this variable spacing is shown exemplarily in the form of multi-spacing studs SD-1, SD-2 etc. which will be understood as insertable (by means not shown) conjunctively between strips LB, the latter being mounted on bracket A etc. to be slideable therealong, resiliently opposed by take-up spring SA. Studs SD may be mounted conventionally in casing CS so as to be adjustably projectible into the interelectrode gaps between strips LB to elfect such line-spacing adjustments. That is, at various, graduated, penetration-distances studs SD (one between each strip LB, in parallel) are turned, in stepped-fashion with each step corresponding to the location of a different spacing distance, these turned-steps comprising annular portions of successively increas'mg diameter, and mounted in registry. It will be understood that studs SD are to be shifted (inserted) by one or more stepped-turns into these gaps and to thereby evenly spread electrodes LB farther apart, an equal line-spacing, the entire array tending to swell (spread) by the cumulative increase in spacing, this being taken up, for instance, on both sides of the overall array by opposed springs SA, SA (latter not shown). Of course, with such a change in spacing, the medium DM etc. will have to be re-registered with array PIR (e.g. since its top line will now assume a different position with respect to LB-1, etc.) by known means.

The typical operation of such a modified character strip array will be better understood with reference to the schematic operative showing in FIG. 3 Where an array of character strips PR, like PR in FIG. 4, is understood as present and operating similarly, being disposed operatively adjacent a cooperating ground plane GP (or crossoriented matrix of column-electrodes similar to function to electrodes 1-8 in FIGS. 1 and 2) with a suitable dielectric medium DM presented therebetween for selective imaging. Medium DM is shown herein continuous strip form, being transported by a pair of rollers for serial-imaging as explained with reference to FIG. 5. The variable-imaging station comprising arrays PR'GP will, of course, provide the'same variable alpha-numeric imaging on DM as aforedescribed and, optionally, may, if desired, be preceded by a downstream fixed-form imaging station, indicated schematically at F. After imaging, strip medium DM will be understood as continually advanced to be developed at toner station T and thereafter brought into copy-transfer relation with a copy medium CP, advanced by a suitable drive means P, indicated (by arrow P-S) as selectively so related with DM, for instance, to thereby allow multiple circulations of DM before this transfer.

Now, according to an advantageous feature of this arrangement, exemplified operatively in FIG. 5, as medium DM (DM) begins to be advanced past imaging array PR (or PR), it will pass with the first print-line thereof in prescribed registry with the first strip LB-1 so that 'as successive columns of this 'first line progress along the length of strip LB-11, a character-image in a particular column may be generated when that column registers with the associated character pattern (on LB1). At that time, character-strip LB-l will be understood to ha e been pre-energized (with part of the imaging potential) while the orthogonal column-electrode at that columnposition (not shown, but assumed as analogous to electrodes 1-8 in FIG. 2 etc.) will at that time be synchronously energized (pulsed with complementary potential) so as to thus elfect an imaging discharge to that portion of the dielectric, thereby creating the latent electrostatic print-image as before. Thus, when the first line portion of DM has been imaged (when it has traversed the length of LB'1) an electrostatic image of the appropriate character to be printed will be present at each column-position thereof. According to this feature, such imaging will proceed line-by-line and serially, so that the second printline begins its imagining scan past array PR (that is, strip LB-2 thereof) just after the imaging of the first line has concluded (serial mode as opposed to recirculating parallel imaging above). Serial imaging of the third and successive lines will proceed accordingly as is schematically indicated on DM in FIG. 5 (different font styles also indicated; both between lines and within a line). It will be apparent that given a prescribed medium speed and character-font separation (i.e. inter-character separation on each strip LB; justification control) may be conveniently controlled simply according to the timing of column-electrode energization. Like media MS in FIG. 1 etc. which was imaged line-by-line on the same pagesegment of a dielectric, medium DM in FIG. 3 (or DM, both being continuous, however, unlike MS) may be imaged to present an entire page-image along a prescribed segment thereof (e.g. SP-l for page one; SP-Z for page two, etc). Of course, synchronizing means must be provided or known in the art (e.g. strobe means using magnetic etc. strobe marks sm to track the page positioncf. FIG. 5). In this manner, medium DM is swept past font-plane PR, once for each line in a particular page (or pages, DM, being only as long as the required pages demand) and is then developed at toning station T, conventionally, after the final line is imaged; thereafter copy medium CR being brought into transferrelation with DM (roll P advanced along direction P-S then).

This system is rather versatile and one may vary this serial-parallel imaging mode by imaging serially-byline along DM, and after toning, transfer to CR in a serial-to-parallel mode. This avoids the recirculation of DM though it uses much more of its length and requires recirculation of copy CR together with registration thereof with the page image on DM (for all lines thereof); this being feasible with means known in the art.

DIELECTRIC DRUM As an alternate to the foregoing electro-printing embodiments, and especially by way of indicating another hollow type roll configuration of character font, the embodiment shown in FIGS. 6 and 7 will now be described. According to another feature of the invention, this arrangement comprises a concave cylindrical fontplane defined by an array MT of individual raised-font character electrodes MT-C (only an exemplary few thereof being shown with a full character-set being understood), each character therein being electrically separate, preferably (unlike the foregoing embodiments). According to another feature of this embodiment, this fontarray is arranged in operative imaging relation with a dielectric-coated imaging drum DD, rotatably mounted to be concentrically within array MT and to present a thin dielectric coating DDC in operative imageable relation therewith. Drum DD is also operatively associated with a toning roll 6T, an erasing roll 6-CL and a copytransfer roll 6-1. Roll 6I selectably presents copy (paper) media 6-CP in transfer relation with dielectric DDC, after imaging and toning thereof, in the manner aforedescribed. This electro-printing system will be assumed as constructed and operating as a functional equivalent to that shown in FIG. 1 etc. except for the below-noted modifications.

One important modification, and another feature of the invention, is that this hollow-type-roll array MT of character-electrodes is arranged to make each individual electrode MT-C electrically independent of all others, each being selectively energized by an associated individual connector T (e.g. TA-1 going to the A electrode in the first column, i.e. in CL-1). Of course, array MT presents a complete set of such electrodes (all alpha-numeric characters) along each column, there being as many electrode columns as there are columns to be Drinted (i.e. print-positions on Drum DD and on copy media 6-CP). The electrodes for each character will be As indicated in FIG. 7, connectors T (e.g. a 132 by 64 array of connectors for 132 print columns with 64 differ ent character fonts) are coupled to a Matrix Select means (functionally indicated only) as understood by those skilled in the art; for instance, comprising a memorycontrol unit for a high speed computer-coupled printer, being adapted for impressing a print-pulse voltage on a particular character electrode terminal at a particular print-column position when that column portion of dielectric DD-C is image-registered with that electrode (corresponding to selected character to be printed there, as above).

In one advantageous mode of operating this system, a particular (variable) angular sector sec (indicated in phantom) of coat DDC is appropriated for imaging a particular print-line along one radial-strip thereof. Then, as sector sec is swept past successive character-rows r-1 to r-n of imaging matrix MT, an imaging potential may be applied to the appropriate character electrode along each respective column CL-1 through CL-n as the corresponding character-rows r pass by, with the next lineimaging being preferred thereafter. Sector sec may be variable, for instance, so that successive print-lines may be generated in relatively close-succession with the imaging of a following line beginning hard upon an indication (signal) of imaging-complete for a subject line on drum DD, e.g. so as to dispense with waiting for the passage of this sector sec past the last character-row (e.g. for character Z), unless that character is to be printed.

Thereafter, the so-imaged print-line will be toned at station 6-T, which may comprise a roll-toner arrangement, a magnetic brush developer or the like as known in the art. Following this, with drum DD kept rotating constantly if desired, the so-toned image-line is then brought into transfer-relation withcopy roll 6I (e.g. contact with copy paper 6-CP thereon) so as to transfer the toned image to medium CP. Successive copies may be made by recirculating this toned line-image on DD for a second complete cycle without erasing, imaging or necessarily retoning (if such a time delay can be tolerated for this), therewhile disabling the erase station 6-CL etc. for this period and re-toning at 6-T if desired, etc. The tonerimage may be fused on CP in a conventional manner such as by heating at copy fuser station CF as understood in the art. Thereafter, the residue of the toned image on drum DD will normally be swept past erase station 6-CL for cleaning (toner removal) and electrostatic erasing (image-neutralizing) as known in the art. Of course, a plurality of lines may also be imaged for subsequent simultaneous development and copy-out where the associated complications can be tolerated, such as an appropriately large memory and high speed switching means, as known in the art.

In summary, it would appear that the aforedescribed invention provides improved electro-printing arrangements including novel, electrostatic imaging features, especially. In particular, it teaches a novel concave imaging plane (hollow type roll) array of raise-font character electrodes. More particularly, such an imaging plane as aforedescribed may take the form of an array of parallel like-character-strip electrodes and, where desired, a co- 12 plicity and convenience than conventional charged typeroll arrangements. It will also be apparent that a special feature of such an electrode array is that it may aptly be arranged to advance an imaging dielectric columnby-column (rather than row-by-row) past such like-character electrode strips and accommodate a simplified bythe-row energizing of ground-electrodes, thus simplifying electrode selection, decoding means, memory means, terminal connections and the like; Workers in the art will recognize how fast such non-impact printing systems can operate; being limited by little more than the medium transport speed and the time necessary to impress an electrostatic image without distorting (e.g. smearing) it.

Workers in the art will recognize that modifications and re-arrangement of the aforegoing novel features may be contemplated within the scope of the claims. More particularly, it will be recognized that the feature of electrostatic printing with such a concave planar array of fontelectrodes may be otherwise implemented. For instance, such an array may be itself selectively toned (powder supply swept past electrodes, such as by drum-sector, to be selectively attracted to printing-electrodes only) and then a conductive carrier (e.g. metallic drum sector charged to attract powder from this font) be advanced therepast so as to pick-up the powder-patterns and thus carry powder-images of the print-characters fordownstream copy-transfer of a given line of print. This carrier could likely be followed by cleaning means preparatory to so printing the next line. Many of the foregoing novel features may be combined in ways other than those described. For instance, where inner transport drum 1-8 (in the embodiment of FIG. 1) is shown as preferably comprised of (ground) electrode strips and, conversely, where drum DD (in the embodiment of FIGS. 6 and 7) is shown as preferably comprising a continuous (grounded) conductive surface, these features may evidently be interchanged in some instances. For instance, drumD=D may alternatively comprise an array of conductive strips, each coated with a dielectric DD-C, the Matrix Select means thus being simplified and the hub-commutator means, step-charging means, etc. provided to operate DD in the aforedescribed manner of 1-8 (though such commutation etc. is usually considered less desirable).

While in accordance with the provisions of the patent statutes,- there have been illustrated and described, the best forms of the invention known, it will be apparent to those skilled in the art that changes will be made in the apparatus described 'without departing from the spirit of the invention as set forth in the appended claims and that in some cases, certain features of the invention may be used to advantage, or modified, or substituted-for, without a corresponding change or substitution in related features.

What is claimed as novel and to be appropriated by Letters Patent is:

1. The combination in an electro-printing system including an electro-static imaging station comprising a stationary font-matrix having an array of raised-font character electrodes arranged in prescribed rows and col- -umns along a'cylindrical electrode plane, said array further comprising parallel, aligned sets of like-character font-electrodes electrically coupled so that each set is electrically chargeable in common and comprises like-character electrodes disposed along a respective column of said cylindrical electrode plane, each set of electrodes thus presenting a linear array of identical raised-font patterns at respective column-positions along this plane, each electrode pattern corresponding to a prescribed character symbol;

said system also including a transport drum rotatingly disposed to be concentric within said electrode plane and arranged to present a prescribed'transport surface in near-tangency thereto, said drum comprising transport means including ground electrode surface means having prescribed gap separation with said 13 electrode plane for advancing separate dielectric media engaged along this surface means, each of said media including a dielectric surface adapted to accept a charge image of a so energized one of said character electrodes;

switching control means adapted to apply high voltage imaging pulses to a selected one of said electrode sets in common for image generation at the associated column position thereof at the time of registry of the associated portion of the dielectric surface destined to image this character;

image treatment means adapted to develop the image on such so-imaged dielectric portions and to copytransfer the so-developed image to prescribed copy media; and,

means for injecting said dielectric media into said engagement with the surface means of said drum electrode and means for abstracting said media there from after a selectable number of rotations past said matrix, presenting said media then to said copytransfer means.

2. The combination as recited in claim 1 wherein said transport drum and abstracting means are controlled to rotate said media portions past said matrix repeatedly, once for each line of print images; and wherein said control means is adapted for charging said electrodes in a line-by-line imaging manner, in synchronism with this transport mode.

3. The combination as recited in claim 2 wherein said drum is adapted to receive unit record dielectric media for advancement a selectable number of times past the font matrix, in prescribed alignment therewith; and wherein said control means is adapted to track the recirculation of such a medium for synchronized charge-imaging thereon.

4. The combination as recited in claim 3 wherein said media are engaged by said drum for recirculating transport past said matrix in a sidewise, column-by-column mode; and wherein said ground strips are individually charged in prescribed order by said charging means and synchronized with said transport and said control means so as to elfect roW-by-row imaging on said media, one row with each recirculation; wherein is also included a stationary format-electrode means configured in a prescribed raised pattern along a format-image plane so as to confront said media in selective electrostatic imaging relation along the transport path thereof in prescribed registration with the intended locus of the aforesaid variable character-imaging pattern contemplated from said matrix; wherein said drum is adapted to receive unit record dielectric media for advancement past the front matrix a selectable number of times and in prescribed alignment therewith, vacuum retention means being provided to engage said media against said drum during said advancement; and wherein said control means is adapted to track the recirculation of such a medium for synchronized charge-imaging thereon.

5. The combination as recited in claim 2 wherein said transport surface comprises a set of parallel ground-strips spaced regularly along said surface in registry with prescribed print-rows and relatively orthogonal to said electrode columns, said strips presenting surfaces to define a ground plane which is concentric 'within and spaced a prescribed gap from, said cylindrical electrode-plane being parallel thereto; and wherein is included selective, charging means coupled to each said ground-strip in parallel and adapted for selective charging of the strips in prescribed order and in synchronism with successive revolutions of a subject dielectric imaging portion past said fontmatrix, thereby to uniquely enable a prescribed line-byline imaging with selected character-electrodes.

6. The combination as recited in claim 5 wherein said media are engaged by said drum for recirculating transport past said matrix in a sidewise, column-by-column mode; and wherein said ground strips are individually charged in prescribed order by said charging means and synchronized with said transport and said control means so as to effect row-by-row imaging on said media, one row with each recirculation.

7. The combination as recited in claim 5 wherein said sets of character electrodes, each, comprise an integral linear conductor strip having said identical raised-font character patterns spaced therealong.

8. The combination in an electro-printing system including an electrostatic imaging station comprising a stationary concave font-matrix having an array of raised-font character electrodes arranged in columnar sets of like character along a prescribed cylindrical electrode plane;

said system also including a transport drum rotatingly disposed to be concentric within said electrode plane and arranged to present a prescribed transport surface in near-tangency thereto;

recording media comprising a thin dielectric coating on said drum having a prescribed image portion adapted to be rotated past said matrix, one rotation for each image-row segment thereon;

switching control means arranged to apply a prescribed select potential to a prescribed one of saidcolumnar electrode sets for inducing imaging of the associated character in a prescribed row-by-row manner along successive ones of said image-row segments;

means to impress a prescribed ground potential selectively upon successive ones of said image-row segments to affect imaging conjunctively with said select potential in accordance with this row-by-row manner;

image treatment means adapted to develop the image on said so-imaged dielectric portions and to copytransfer the so-developed image to prescribed copy media; and,

dielectric cleaning means downstream of said treatment means for removing developer residue and for neutralizing electrostatic images on said dielectric after copy-transfer. 9. The combination in an electro-printing system including electrostatic imaging apparatus comprising a concave font-matrix having an array of raised-font electrodes arranged to be kept stationary along a prescribed cylindrical imaging plane, said raised-font electrodes comprising character-imaging surfaces disposed along a prescribed curved electrode plane, concentric with said imaging plane and spaced a prescribed distance therebeyond;

said apparatus further comprising a cylindrical drum mounted to be continuously rotated so as to present a prescribed conductive surface along a prescribed cylindrical ground-plane, said surface being arranged to present a prescribed ground potential and adapted to continuously advance a dielectric cylindrical media plane in imaging-relation with said imaging plane;

means to rotate said drum at a prescribed constant angular velocity;

charging means operative responsive to this rotational motion to synchronously apply selected printing potentials to. a selected one of said character electrodes representative of the symbol to be printed in alignment with the associated portion of said dielectric surface whereby a latent electrostatic image of the selected character is produced thereon, said charging means including a memory bank with successive registers for each print position, each corresponding to print-line locations along said dielectric surface and adapted to store character indicating signals therein representing characters along associated print-line locations; select means for indicating the registration of a selected character-portion of said dielectric surface with a character electrode corresponding to the selected character to be printed there and responsively enabling charging of this electrode by said charging means, said imaging dielectric surfacebeing adapted to sustain said electric charges in a prescribed manner; developer means arranged downstream of said imaging means and in operative relation with said imaging surface for developing a powder image thereon of the latent image so impressed; and,

transfer means arranged downstream, in turn, of said developer means and also arranged in operative, transfer relation with said developed imaging surface so as to present a copy media continuously adjacent thereto for transfer of the powder image.

10. The combination as recited in claim 9 wherein said dielectric surface comprises a coating of dielectric material on said drum at least on recording portions thereof.

11. The combination as recited in claim 9 wherein said dielectric surface comprises the surface of moving electrostatic recording media adapted to be engaged and advanced by said drum and adapted to be recirculated thereby a prescribed selected number of times past said imaging means.

12. Electrostatic imaging apparatus comprising a concave font-matrix having an array of raised-font electrostatic imaging electrodes arranged to be kept stationary along a curved electrode plane in print-adjacency to a prescribed inner media plane along which media are to be advanced for printing, said electrodes adapted to project image inducing charges upon media passing along said media plane, said electrodes further being arrayed in parallel along a prescribed matrix of rows and columns to present electrode font-surfaces along said prescribed curved electrode plane, a conductive carrier member adapted to present a prescribed dielectric recording layer along a prescribed cylindrical image plane at a prescribed velocity;

said image plane being concentric with said electrode plane and spaced a prescribed gap radially therefrom in imaging relation with such electrodes being given a predetermined imaging potential therebetween, said electrodes being thus selectively chargeable to impress an electrostatic image on a confronting portion of said layer, such images corresponding, each, to the character to printed at the print-column and printrow location represented by that portion; and,

signaling means adapted to apply, selectively, a prescribed electrode potential to a selected one of said electrodes when the character image thereof is to be impressed on said location of said passing dielectric surface whereat the corresponding character is to be printed, said potential being effective for impressing sai'd imaging potential to effect said imaging according to an ionizing field discharge across said gap between said confronting dielectric and electrode surfaces.

13. Electrostatic image printing apparatus including Tesi-imaging means adapted to selectively impress prescribed electrostatic images on prescribed dielectric surfaces comprising an array of raised-font electrodes, said array providing a stationary concave imaging matrix means adapted to present a matrix of raised-font character electrodes at prescribed index points along a cylindrical electrode plane and associated control-charging means adapted to selectably energize said electrodes so as to generate an associated electrostatic character-image on the confronting portions of such dielectric surface as the latter is advanced therepast along a prescribed imaging plane, said imaging plane being concentric with said electrode plane and in imaging relation therewith;

transport means for so advancing said surfaces at constant velocity continuously along said imaging plane, said transport means including conductive electrode surface means adapted to engage said dielectric surfaces and to establish a ground potential in conjunction with said electrode plane for cooperatively generating said images;

means for toning said me-dium, disposed downstream of said matrix means; and,.

means for transferring said toned medium to copy media downstream of said toning means;

said charging means including synchronizing means responsive to the said surface advancing past said matrix means whereby to control said electrodeenergizing to' be synchronous with this advance.

14. The combination as recited in claim 13 wherein is also included a stationary format-electrode means configured in a prescribed raised pattern along a format-image plane so as to confront said media in selective electrostatic imaging relation along the transport path thereof in prescribed registration with the intended locus ofthe aforesaid variable character-imaging pattern contemplated from said character electrode matrix.

15. Inan apparatus for print-imaging selected raisedfont symbols on prescribed media advancing along a predetermined print-plane in a prescribed imaging-direction, the combination therewith of:

a raised-font imaging array comprising a plurality of multi-font electrically separate conductor strips arranged to be held in prescribed parallel alignment with said plane, and imagingly-adjacent thereto, each said strip including a like plurality of different raised-font portions therealong, each said portions being identical to, and in registry with, a related portion on the other strips, and a plurality of column electrodes disposed on the opposite side of said plane, each said column electrode being disposed orthogonally to said strips and in alignment with arespective one of said related portions on said strips.

16. The combination as recited in claim 15 wherein said portions comprise a plurality of equivalent font-sets, each set comprising a plurality of related font-portions, whereby said media may be advanced therepast to be characterimaged according to a selectable font-style characteristic of a prescribed one of said sets, as well as according to a selectable character-image within a set.

17. The combination as recited in claim 15 wherein said array includes a plurality of like spacer means, each adapted to be adjustably inserted between a respective pair of said strips for establishing one of a selectable number of strip-spacings; plus an associated resilient means for biasing said strips into engagement with said spacer means.

18. The combination as recited in claim 17 wherein said spacer means each comprises a notched stud having annular segments of increasing width corresponding to increas ing strip spacings; said studs being mounted to be conjunct-ively inserted between said respective strips for selectable equi-spacing positioning thereof.

19. The combination as recited in claim 15 wherein said strips .comprise parallel raised-font conductors arranged to be charged as a whole by selective charging means so as to Tesiimage selected ones of said font-portions on a prescribed registered portion of said passing media.

20. The combination as recited in claim 19 wherein said media comprise dielectric web means adapted to be advanced and recirculated a prescribed number of times longitudinally across said strip array, one time for each line-imaging thereby; wherein charging means are also provided to impress imaging potential synchronous with said line-imaging; and wherein image-developing and copytransfer means are also provided for generating readable print-out of the images so formed.

21. The combination as recited in claim 20 wherein said font-portions comprise a plurality of equivalent font-sets, each set comprising a plurality of related font-portions, whereby said media may be advanced therepast to be character-imaged according to selectable font-style characteristic of a set as well as according to a selectable character-image within a set; 'wherein said array includes a plurality of like spacer means, each adapted to be adjustably inserted between a pair of said strips for establishing one 17 18 of a selectable number of strip-spacings; plus an associated 3,289,209 11/ 1966 Schwertz et a1 346-74 resilient means for biasing said strips into engagement 3,124,067 3/1964 Morgan 101-394 with said spacer means; each said spacer means compris- 3,289,209 11/1966 Schwertz et al. 346-74 ing a notched stud having annular segments of increasing width corresponding to increasing strip spacings; said 5 FOREIGN PATENTS studs being mounted to be conjunctively inserted between 182,742 1 966 U.S.S.R. 101-116 said respective strips for equi-spacing positioning thereof.

BERNARD KONICK, Prrmary Examlner References Cited G. M. HOFFMAN, Assistant Examiner UNITED STATES PATENTS 10 2,586,047 2/1952 Huebner 101-116 101 1 391 396 2,758,939 8/1956 Sugarman 117-175 2,816,505 12/1957 Michelson 101-391 

